1) Deetz, James. (1977). In Small Things Forgotten: The Archaeology of Early American Life. Doubleday.
2) Ensminger, Robert F. (1992). The Pennsylvania Barn Book. The John Hopkins University Press.
3) Glassie, Henry. (1968). Pattern in the Material Folk Culture of the Eastern United States. Philadelphia: University of Pennsylvania Press.
4) Litchten, Frances. (1946). Folk Art of Rural Pennsylvania. New York: Scribner's.
5) Long, Amos Jr. (1972). The Pennsylvania German Family Farm. The Pennsylvania German Society.
6) Stair, J. William. (1954). Brick-End Barns of the Pennsylvania Dutch.
7) Stevens, Sylvester K. (1964). Pennsylvania Birthplace of a Nation. Random House.
8) Yoder, Don. (1989). Hex Signs. New York: E.P.Dutton.
9) http://www.mindspring.com/~rmastin/symbol.html
10) http://www.state.pa.us/PA_History/quaker.htm
11) http://www.nga.gov/collection/gallery/iadpenn/iadpenn-main4.html